<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let score = Number (prompt('请输入你的成绩:'))
        if(score > 90){
            alert('A')
        }
        else if(score > 80 && score <= 90){
            alert('B')
        }
        else if(score > 70 && score <= 80){
            alert('C')
        }
        else if(score > 60 && score <= 70){
            alert('D')
        }
        else {
            alert('E')
        }
    </script>
</body>
</html>